参数资料
型号: ISL29023IROZ-EVALZ
厂商: Intersil
文件页数: 10/14页
文件大小: 0K
描述: EVALUATION BOARD ISL29023IROZ
标准包装: 1
传感器类型: 灯光,数字式输出
传感范围: 64000Lux
接口: I²C,SM 总线
灵敏度: 540nm
电源电压: 2.25 V ~ 3.63 V
嵌入式:
已供物品:
已用 IC / 零件: ISL29023
ISL29023
Upper Interrupt Threshold Registers
TABLE 14. INTEGRATION TIME OF n-BIT ADC
(Address: 0x06 & 0x07)
TABLE 13. INTERRUPT REGISTER BITS
R EXT (k ? )
499**
n = 16-BIT
90ms
n = 12-BIT
5.6ms
n = 8-BIT
352μs
n = 4-BIT
22μs
Reg.
Register Bits
**Recommended R EXT resistor value
Range = ------------------ × Range ( k )
Addr DFLT
NAME (Hex) B7 B6 B5 B4 B3 B2 B1 B0 (Hex)
INT_HT_LSB 0x06 TH7 TH6 TH5 TH4 TH3 TH2 TH1 TH0 0xFF
INT_HT_MSB 0x07 TH15 TH14 TH13 TH12 TH11 TH10 TH9 TH8 0xFF
The upper interrupt threshold registers are used to set the upper
trigger point for interrupt generation. If the ALS value crosses
above or is equal to the upper threshold, an interrupt is asserted
on the interrupt pin and the interrupt flag. Registers INT_HT_LSB
(0x06) and INT_HT_MSB (0x07) provide the low and high bytes,
External Scaling Resistor R EXT for f OSC and
Range
The ISL29023 uses an external resistor R EXT to fix its internal
oscillator frequency f OSC and the light sensing range, Range. f OSC
and Range are inversely proportional to R EXT . For user simplicity,
the proportionality constant is referenced to 499k ? :
499k Ω (EQ. 5)
R EXT
f OSC = ------------------ × 725 kHz
respectively, of the upper interrupt threshold. The high and low
bytes from each set of registers are combined to form a 16-bit
threshold value. The interrupt threshold registers default to 0xFF
on power up.
Applications Information
Calculating Lux
499k Ω
R EXT
ADC Output in IR Sensing
The ISL29023’s ADC output codes, DATA, are directly
proportional to the IR intensity received in the IR sensing.
DATA IR = β × E IR
(EQ. 6)
(EQ. 7)
The ISL29023’s ADC output codes, DATA, are directly
proportional to lux in the ambient light sensing.
E cal = α × DATA
(EQ. 1)
Here, E IR is the received IR intensity. The constant β changes with
the spectrum of background IR noise, such as sunlight and
incandescent light. The β also changes with the ADC’s range and
Range ( k )
Here, E cal is the calculated lux reading. The constant α is
determined by the Full Scale Range and the ADC’s maximum
output counts. The constant is independent of the light sources
(fluorescent, incandescent and sunlight) because the light
sources’ IR component is removed during the light signal
process. The constant can also be viewed as the sensitivity (the
smallest lux measurement the device can measure).
α = ---------------------------- (EQ. 2)
Count max
Here, Range(k) is defined in Table 8. Count max is the maximum
output counts from the ADC.
The transfer function used for n-bits ADC becomes:
resolution selections.
Noise Rejection
Electrical AC power worldwide is distributed at either 50Hz or
60Hz. Artificial light sources vary in intensity at the AC power
frequencies. The undesired interference frequencies are infused
on the electrical signals. This variation is one of the main sources
of noise for the light sensors. Integrating type ADC’s have
excellent noise-rejection characteristics for periodic noise
sources whose frequency is an integer multiple of the conversion
rate. By setting the sensor’s integration time to an integer
multiple of periodic noise signal, the performance of an ambient
light sensor can be improved greatly in the presence of noise. In
order to reject the AC noise, the integration time of the sensor
E cal = --------------------------- × DATA
Range ( k )
n
2
Here, n = 4, 8, 12 or 16. This is the number of ADC bits
programmed in the command register. 2 n represents the
(EQ. 3)
must to adjusted to match the AC noise cycle. For instance, a
60Hz AC unwanted signal’s sum from 0ms to k*16.66ms
(k = 1,2...k i ) is zero. Similarly, setting the device’s integration
time to be an integer multiple of the periodic noise signal greatly
improves the light sensor output signal in the presence of noise.
maximum number of counts possible from the ADC output. Data
is the ADC output stored in the data registers (02 hex and 03
hex).
Integration and Conversion Time
The ADC resolution and f OSC determine the integration time, t int .
Suggested PCB Footprint
It is important that users check the “Surface Mount Assembly
Guidelines for Optical Dual Flat Pack No Lead (ODFN) Package”
before starting ODFN product board mounting.
t int = 2 × -------------- = 2 × ----------------------------------------------
f OSC
n 1 n R EXT
725kHz × 499k Ω
(EQ. 4)
where n is the number of bits of resolution and n = 4, 8, 12 or 16.
Therefore, 2 n is the number of clock cycles. n can be programmed
at the command register 01(hex) bits 3 and 2.
10
FN6691.3
April 25, 2013
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